The present disclosure relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine or their multifunctional machine, and more particularly relates to an image forming apparatus that includes a development device which uses a two-component developer containing a toner and a magnetic carrier and which carries only the toner on a toner carrying member to develop an electrostatic latent image on an image carrying member.
Conventionally, as a development device that develops an electrostatic latent image on a photosensitive drum which is an image carrying member, the development devices of a one-component development method and a two-component development method are known. The two-component development method is suitable for achieving a long life because a developer formed with a toner and a magnetic carrier is used to stabilize the amount of charge for a long period of time. For example, the development device of the two-component development method holds a two-component developer containing a toner and a magnetic carrier, and supplies the developer from an agitation member to a magnetic roller (developer carrying member). The magnetic roller includes a magnet therewithin, and carries, with the magnet, the developer as a magnetic brush on the surface of the magnetic roller and transports the developer to the photosensitive drum by the rotation of the magnetic roller. Furthermore, the development device includes a restriction member which restricts the thickness of the layer of the developer so that the amount of developer transported by the rotation of the magnetic roller to the photosensitive drum is made constant. When the magnetic roller is opposite the photosensitive drum, only the toner of the developer carried on the magnetic roller is supplied to the photosensitive drum, and an electrostatic latent image on the photosensitive drum is visualized as a toner image.
When the restriction member restricts the thickness of the layer of the developer to form the uniform layer of the developer on the surface of the magnetic roller, the toner in the developer is scattered, as minute particles, around the restriction member when scrubbed with the restriction member. The scattered toner is adhered to the surface of the restriction member on the downstream side with respect to the direction of rotation of the magnetic roller, and is gradually deposited.
Hence, a method is known in which in order for the toner deposit adhered to the restriction member to be scrubbed off, a bias between a photosensitive drum and a magnetic roller is turned off, the rotation of the photosensitive drum is stopped and furthermore, the magnetic roller is rotated in a reverse direction to that at the time of image formation.
Incidentally, as a two-component development method other than the development method described above, a development method is known which includes a magnetic roller (developer carrying member) that carries, with a magnet incorporated, a developer containing a toner and a magnetic carrier on its surface as a magnetic brush to transport the carried magnetic brush, a development roller (toner carrying member) that is arranged opposite a photosensitive drum and the magnetic roller, that carries the toner in the magnetic brush transported by the magnetic roller on the surface and that supplies the carried toner to the photosensitive drum and a restriction member that is arranged a predetermined distance apart from the magnetic roller and that restricts the thickness of the layer of the developer on the surface of the magnetic roller, and which carries only the toner on the development roller to develop an electrostatic latent image on the photosensitive drum.